Really? Yes. The Graphics are the key. If people find that the PS4 and 720 aren't large leaps in appearance for their games, then third-party devlopers will be willing to put their games the same way on the Wii U, because of its iPad style controller, which will and kind of already has people attracted, and also can open up new experiences. With third party support, people will probably choose the Wii U for its first party support as the deal-breaker, primarily because of Nintendo's strategy - of course this isn't confirmed, but Nintendo will most likely release a Zelda game and Super Smash Bros. game for the system around the time the PS4 or 720 come out to lure people and seal sales from its competiters.
Yes, Nintendo's online will be just fine. Here's why. Or rather, hre's two reasons why. Or more. Let me just say some of them here. First, obviously, they have or rather will have most of the features PSN and XBL has (minus the trillion apps that Live has of course), but it will have not only Voice Chat and Text Chat, but more importantly, VIDEO Chat. This will add an extra dimension, but the biggest thing is the introduction of MiiVerse. To be able to seamlessly communicate with friends on your controller's screen to ask for tips, comment on things, share achievements, all while your playing your game, or not.
But lets get back to the point. The graphics are a key point. Of Course graphics don't make hardware, but that was the main thing that caused a lack of third party support for the Wii. If it can hold up to the PS4 and Nextbox, then it's gamepad will look much less than a gimmick, people will choose its first-party games as a deal-breaker, and the Wii U can succeed. Nintendo can get their hardcore audience they want, and their console can lead, for the whole generation, in terms of sales, and respect.
Wii U Pro Controller. When you look at history, Nintendo is pretty much just combining their innovative controllers, not exactly copying the 360 controller.